The present invention relates to lifting slings for lifting up a plurality of elongated heavy articles such as products, components, devices, mechanical elements or members, structural materials and particularly pipes, rolls, slabs or the like, to carry the elongated articles to desirable locations and, more particularly, to a lifting sling for lifting up at least one elongated article without the need of assistance of a third person such as a slinging worker or the like. The pipes may be made of metal, plastics or concrete used in various industries, and may be made of steel having particularly high rigidity.
As is generally known, the following means is adopted or taken in cases where various cranes are used to carry loads. That is, normally, a pair of wire rope units are arranged in agreement with a load manually. Then, a pair of hanging rings arranged respectively at proximal ends of the wire rope units are hung on a hook of a crane, to lift up the load.
Incidentally, for the purposes of saving energy or power, increasing the efficiency of the work and increasing safety, a lifting sling for at least one elongated article has been proposed which involves only an operator of the crane and remote-controls of operation of engagement and disengagement of the wire rope units with respect to the load, that is, so-called slinging work.
For instance, a lifting sling for lifting up an elongated heavy article such as a rolling roll or the like is disclosed in Japanese Utility Model Unexamined Publication No. 56-124678. The lifting sling comprises a hoisting element which is detachably suspended from a crane hook. A guiding rod is mounted on the hoisting element and has an end at which a stopper is arranged. A sliding element is loosely fitted about the guide rod movable vertically. A pair of arm elements are pivotally attached to the sliding element. A pair of wire elements are connected between forward ends of the respective arm elements and the hoisting element. A pair of hanging wire elements depend respectively from the forward ends of the arm elements.
The above lifting sling is capable of transporting loads to be carried extremely efficiently, if the loads are specified, and if dimensions and weights of the loads are determined. If the loads are different in dimension from each other and different in weight from each other, however, it is difficult to cope with such loads. In view of this, the inventors of this application have developed a lifting sling which has a wide range of utilization and which is efficient. The inventors have filed an application relating to the lifting sling.
The above-mentioned application has been laid open to public inspection as Japanese Utility Model Unexamined Publication No. 62-186880. A lifting sling disclosed in the Japanese unexamined publication comprises a pair of wire rope units which are detachably suspended from a crane hook. A support rod element is detachably suspended from the crane hook through an attaching element which is mounted on the top of the support rod element. A pair of sliding support arms in the form of a wing are pivotally supported by the support rod element. A pair of operational cylinders are provided which extend between the support rod element and the pair of sliding support arms. An opening guide device is provided which includes a mechanism having a pair of link elements for enabling the pair of sliding support arms to be opened and closed in a symmetrical manner. A remote-controller operates the pair of operational cylinders so as to extend and contract rods of the respective cylinders. The pair of sliding support arms guide the pair of wire rope units so as to be capable of being opened and closed by means of the opening guide device and the remote-controller. Accordingly with the lifting sling, it is possible to remote-control the lifting sling without the necessity of a slinging worker.
The above lifting sling will be described below in detail with reference to FIGS. 25 and 26 of the attached drawings. A pair of detachable wire rope straps 2a and 2b are suspended from a T-shaped crane hook 1. The pair of wire rope straps 2a and 2b are guided by a pair of sliding support arms 3a and 3b arranged in the form of a wing and an opening guide device R subsequently to be described, such that the pair of wire rope straps 2a and 2b are arranged symmetrically to each other and their opening angle is adjustable.
Without assistance of a slinging worker, an operator of a crane (not shown) hangs lower ends 2a.sub.1 and 2b.sub.1 of the respective wire rope straps 2a and 2b around both ends of an elongated article to be carried, for example, around both ends 4a and 4b of a rolling roll 4. Then, the operator lifts up the rolling roll 4 and carries the same to a desirable location. Subsequently, the operator lowers the rolling roll 4 at the desirable location, and operates the opening guide device R. The pair of sliding support arms 3a and 3b in the form of a wing are moved away from each other. The lower ends 2a.sub.1 and 2b.sub.1 of the respective wire rope straps 2a and 2b are disengaged respectively from both ends 4a and 4b of the rolling roll 4. The operator can then immediately begin the subsequent carrying operation.
The pair of wire rope straps 2a and 2b are in slidable engagement with the pair of sliding support arms 3a and 3b, respectively. Accordingly, no unreasonable force is applied to the pair of sliding support arms 3a and 3b and the opening guide device R. In addition, it is possible to cope with elongated articles to be carried having various dimensions or sizes within a permissible or allowable range of opening angle of the pair of sliding support arms 3a and 3b, without assistance of the slinging worker as described above.
Further, as shown in FIGS. 25 and 26, a top of a support rod element 5 is provided with an attaching element 6 which is detachably suspended from the crane hook 1. The pair of sliding support arms 3a and 3b are arranged in the form of a wing. Each of the arms 3a has an end which is pivotally or angularly movably supported by the support rod element 5 through one of a pair of support pivots 7a and 7b.
Since the other ends of the respective sliding support arms 3a and 3b are not restricted or restrained, the pair of sliding support arms 3a and 3b can be moved about the support pivots 7a and 7b, respectively like a wing. Moreover, the pair of sliding support arms 3a and 3b guide the pair of wire rope straps 2a and 2b, respectively. However, the pair of sliding support arms 3a and 3b are not in an engaging relationship to the pair of wire rope straps 2a and 2b such that they are restricted in movement relative to each other. Thus, members or elements designated respectively by the reference numerals 3a and 3b are called sliding support arms in the form of a wing.
A pair of operational cylinders 8a and 8b are pivotally attached to the bottom of the support rod element 5 and the respective sliding support arms 3a and 3b. A joint 10 is loosely fitted in a guide groove 9 which is formed in a lower portion of the support rod element 5. A pair of link plates 11a and 11b have one of their ends pivotally connected to upper portions of the pair of sliding support arms 3a and 3b, respectively. The other ends of the respective link plates 11a and 11b are pivotally connected to the joint 10 which is movable along the guide groove 9.
When the pair of operational cylinders 8a and 8b are operated, the pair of sliding support arms 3a and 3b can be moved toward and away from each other symmetrically about the longitudinal axis of the support rod element 5 due to cooperation between the joint 10 and the guide groove 9 such that the angle between the pair of operational cylinders 8a and 8b is adjustable. This angular movement of the pair of sliding support arms 3a and 3b is called the capability of opening angle. A mechanism composed of the pair of operational cylinders 8a and 8b and the pair of link plates 11a and 11b is called the opening guiding device R which enables the pair of sliding support arms 3a and 3b to be opened and closed in symmetrical relation to each other.
As illustrated in FIG. 25, an air line 12 is connected to the pair of operational cylinders 8a and 8b (in this example, air cylinders) to supply air thereto. The air line 12 is connected to a remote-controller (not shown) which is arranged within a crane operation room. Of course the pair of operational cylinders 8a and 8b may utilize any suitable power sources such as a hydraulic source or an electric source, instead of the pneumatic source. The remote-controller is well-known, and the description thereof will be omitted.
Furthermore, two pairs of guide connecting plates 13 and 14 are provided respectively for the pair of sliding support arms 3a and 3b. A pair of slip off preventing hook units 15 and 15 are also provided respectively for the pair of sliding support arms 3a and 3b. Each of the pair of slip off preventing hook units 15 and 15 is composed of a pair of hooks, as shown in FIG. 26.
As described above, in the lifting sling constructed as mentioned previously, loads are applied only to the pair of wire rope straps 2a and 2b, but no loads are applied to the pair of sliding support arms 3a and 3b and the opening guide device R. Accordingly, it is unnecessary to use members or elements which are high in strength. Thus, the lifting sling can be designed economically. In addition, the lifting sling is easy in handling as compared with a conventional one. Replacement of the pair of wire rope straps 2a and 2b with respect to the crane hook 1 is also easy and simple and is high in operability. However, the inventors of this application have applied the above lifting sling to the lifting of various elongated articles to be carried, and have experienced that the following tasks are necessary.
That is, in the case of elongated heavy articles such as pipes or slabs having their lengths of 7 m to 15 m, two crane hooks are required, and two lifting slings cooperating together are used to lift up the elongated articles. Thus, the operation is difficult, and the posture of the elongated article or load becomes unstable. Moreover, in an aspect of the installation, the lifting sling is high in cost.
Apart from the above, in various industries, many elongated pipes made of various materials and in various forms are used for various purposes such as structural elements and transportation of various gasses and liquids. There are many cases where large cranes are utilized in manufacturing and processing of pipes, and mounting, transportation, storage and so on of the pipes. In this case, various pipe lifting slings have been developed in order to provide safety of operation and to improve the efficiency thereof.
For instance, a lifting sling is disclosed in Japanese Patent Publication No. 51-47219, in which, when pipes are suspended by hooking ropes having their hooks hung from a beam hook, the pipes are automatically disengaged from the hooking ropes by an arm expansion device. Further, Japanese Patent Unexamined Publication No. 52-133653 discloses a lifting sling in which a mobile hook vehicle is mounted on a hanging beam to automatically perform slinging work of pipes.
The inventors of this application have conducted working in which an overhead travailing crane is used to carry or transport various pipes, particularly, elongated steel pipes having a large internal diameter. The inventors have known or found that the conventional lifting slings have no devices or instruments which are adequate for efficient and safe transportation of many pipes.
For example, the lifting sling disclosed in the aforesaid Japanese Patent Publication No. 51-47219 is efficient for slinging of two or three pipes having relatively small open diameters. When many pipes having large internal diameters are transported, however, the lifting sling is complicated in structure and, simultaneously, operation of the lifting sling is also made difficult.
Further, the lifting sling disclosed in the above Japanese Patent Unexamined Publication No. 52-133653 is capable of automatically slinging pipes regardless of their dimension, and is superior for energy saving. In order to carry a plurality of pipes simultaneously, however, installation of the lifting sling is complicated, and also synchronous lifting operation is difficult in remote-control.